I'm fairly new at this but I can see myself being in the same corner as your in-laws. It's not that I don't want to "help" my son and give him everything I can, but I am learning that almost everything I give while he is using is somehow converted into enabling his addiction. The best thing I can do for my son is nothing right now and hold my boundaries firm. Now that your boyfriend is clean, your in-laws might be attempting to make up for lost time, loving him in the way they only know how and always wanted. Admittedly, their behavior might be unhealthy, but this can explain the radical change in behavior.
I'm not sure if you can comprehend a drug addict's parent's corner. Just one aspect of my pain, every time I wake up in the middle of the night for no apparent reason, which seems to be more frequent as I age, I wonder if I just received a sign that my son has died. I experience this insomnia several times a week. My son has been to ER six times this year. It hurts to care and this particular pain just scratches the surface.